T-56 fluid choice?

[69hugger]

Guys,
I drained the fluid in my T-56, and need to refill. The big orange label on my trans says to use Dexron III fluid. This is for street use.
Like most of us, part of me says to follow the instructions, part says to use something "better".
There are many choices for newer formulations, synthetics, etc. I know synthetics are SUPPOSED to be better, but my experience has shown them to leak more than conventional fluids, at least in old motors & rear ends.

Looking for your opinions on what to refill with & WHY.

THANKS!

Bill